To achieve high gear ratios in the range of between 1:50 and 1:150 or higher, gear units with many toothed wheels or other types of relatively space-demanding gear means are normally required. In many kinds of operation where only a small space is available, for example in articulated robot arms, this is an awkward drawback. The present invention relates to a gear unit which is built into a small space around the outgoing main shaft of the gear.
From U.S. Pat. No. 1,802,112, a differential-type reduction gear is previously known, by means of which very high gear ratios can be obtained. A drawback of this gear is that it comprises eight toothed wheels, which entails a high production cost and a large space requirement.